The basic manual wheelchair, its drive wheel design unchanged for decades, neglects the varying needs of wheelchair users. Disabled persons often need greater mechanical advantage and control than what the conventional chair offers. Those with less arm strength may find it difficult to remain independently ambulatory in a manual wheelchair. These persons can be severely challenged by uneven terrain (grass, gravel, sand, etc.), hills, curbs, door jams, thick rugs and even wheelchair ramps. The two-speed manual wheelchair wheels to be developed by this project will offer all types of patients regardless of strength the ability to shift to an advanced self-locking lower gear (higher mechanical advantage) drive when needed. This self-locking feature will give advanced control of the wheelchair under difficult situations and will work going up as well as down hills. A wheel quick release mechanism will facilitate convenient storage in auto trunks, etc. during transportation. During Phase I, the basic hypocyclic drive design (see figure I and 2) will be developed, tested on disabled persons and refined to give best performance. Phase II will be used to build preproduction prototypes and to accomplish full scale safety and clinical evaluations prior to marketing the device in Phase III. PROPOSED COMMERCIAL APPLICATION: The two-speed manual wheelchair wheels to be developed under this proposal could become the preferred type wheel for most manually powered wheelchairs.